The present invention relates generally to improvements in communication systems and components thereof, and specifically to the provision of an insular waveguide transmission line and components incorporating such a transmission line including passive signal processing components such as couplers, filters, and mode launchers, and active signal processing components such as oscillators and mixers.
Standard practice heretofore in interconnecting components of communication systems in the 1 GHz to 300 GHz frequency range has utilized metallic waveguide, coaxial, microstrip, stripline, slotline or image waveguide transmission lines. The losses encountered in the use of coaxial, microstrip, slotline, stripline and image waveguide transmission lines increase rapidly as the frequency increases, and as a consequence, at about 10 GHz and above the losses encountered in such transmission lines during propogation of electromagnetic energy are substantial, rendering the system uneconomical. Metallic waveguide and coaxial transmission lines also are not readily used as parts of integrated circuits, i.e., these transmission lines do not have an integrable geometry.
Image waveguide transmission lines consist of a dielectric waveguide mounted upon a conductive image plane. It has been found impracticable in practice to maintain manufacturing tolerances so as to prevent formation of gaps between the dielectric waveguide and the conductive image plane. Even very small gaps between the dielectric waveguides and the conductive image plane have a large effect on the dispersion characteristics, i.e., guide wavelength, of the image waveguide transmission line.
Standard practice at frequencies well above 1,000 GHz including the optical range, has been to utilize bundles of fibers or very thin slabs of dielectric material on a mechanical support. These systems cannot be readily fabricated to form integrated circuits of passive and active circuit elements.